BR112014025805B1 - catalyst for the polymerization of olefins, process for their production and related use - Google Patents

Abstract

CATALYST FOR THE POLYMERIZATION OF OLEFINS, PROCESS FOR THEIR PRODUCTION AND USE. The present invention provides a new process for preparing a catalyst for the gas phase polymerization of olefins, wherein the sequence of addition of components to the catalyst and selection of said components provides a catalyst composition that exhibits a superior hydrogen response, surprisingly a high productivity and an improved activity profile. The catalyst consists of compounds of a Group IV transition metal, Mg, Cl and Al supported on a silica support.

Description

[001] The present invention relates to supported Ziegler-Natta catalysts which are useful in the polymerization of olefin, and more particularly useful in the gas phase continuous fluidized bed and suspension polymerization of alpha-olefins. The present invention details a method for producing these catalysts as well as identifying a method for using them in a gas phase or suspension process to produce polyethylene.

[002] Ziegler-Natta type catalysts are well known and have been used since the early 1950's. Generally, the catalyst comprises a transition metal compound, typically titanium in valence state 3 or 4 (eg TiCl3 or TiCl4 ) supported on magnesium chloride.

[003] In some cases, catalysts are prepared together with an electron donor, which is used to dissolve MgCl2 and TiCl3 when they are used. This type of formulation teaches from the current disclosure.

[004] Alternatively, catalysts can be prepared from the addition of magnesium chloride to the support and consecutive addition of the Ti species. Again, this type of formulation teaches from the current disclosure.

[005] Alternatively, catalysts can be prepared on a support that is pretreated with the organosilicon compound. Again, this type of formulation teaches from the current disclosure.

[006] The present invention seeks to provide a process for the polymerization of olefin polymers, preferably ethylene polymers characterized in that the catalytic system exhibits a superior response to hydrogen, a surprisingly high productivity and an improved activity profile.

[007] The inventors have unexpectedly revealed that both catalyst activity and hydrogen response can be unexpectedly high using the catalyst of the invention prepared following the order of addition and specific catalyst components.

PREPARATION

[008] The present invention provides a process for the preparation of an alpha-olefin polymerization catalyst composition comprising - in a first stage, the formation of a liquid Mg-M complex (M is a transition metal) in the absence of halogen-containing compound by reacting at least one magnesium compound comprising organic oxygen with at least one transition metal oxygen-comprising compound, - in a second stage, the impregnation of a silica support by means of said liquid Mg-M complex , and - in a subsequent stage, the precipitation of said liquid Mg-M complex on silica by means of a halogenated organoaluminium compound, wherein - during the first stage reaction, the molar amount of transition metal M is added by each mole of magnesium is comprised between 0.06 and 4, and - said silica support has, before impregnation of the liquid Mg-M complex, a residual surface hydroxyl content comprised between 0. 6 and 2 mmol/g silica, preferably between 1 and 1.6 mmol/g silica.

SILICA

[009] The silica support for the catalysts useful in the present invention typically comprises silica having a reactive hydroxyl radical. It is critical according to the present invention that, prior to its impregnation with the liquid Mg-M complex, the silica exhibits a residual surface hydroxyl content of between 0.6 and 2 mmol/g of silica, preferably between 1 and 1.6 mmol/g silica.

[0010] The silica support is preferably spherical and/or spheroidal. For the purpose of the present invention and appended claims, spheroidal morphology means a shape of a sphere, but not perfectly round, especially an ellipsoid shape which is generated by the rotation of one or more ellipses around one of its axes. Thus, for the purpose of the present invention and appended claims, by "spherical and/or spheroidal morphology" means that the silica support exhibits spherical and/or spheroidal morphology. Such spherical and/or spheroidal morphology of said silica support is generally identified by microscopy photos of said support; this is actually how the person skilled in the art can identify the presence of a spherical and/or spheroidal particles.

[0011] The spherical and/or spheroidal silica support can be suitably prepared by spray drying washed and aged hydrogel particles or adjusting the spray of a hydrosol. Such processes are well known in the art and typically result in spherical and/or spheroidal particles. Particle size can be adjusted by selecting conditions. In that invention, the average diameter (volume) of the spherical and/or spheroidal particles measured after drying is preferably from 10 to 250 µm, preferably from 20 to 200 µm and more preferably from 20 to 150 µm. International ISO 13320:2009 ("Particle Size Analysis - Laser Diffraction Methods") may be used to measure said characteristic of the average particle size. Particle diameters are in fact normally measured using light scattering techniques. For example, laser diffraction systems from Malvern Instruments can advantageously be used, for example a Malvern Mastersizer S or a Malvern Mastersizer 2000; such instrument, together with its operational manual, meet or even exceed the requirements established under ISO 13320; the Malvern wet dispersion procedure (Qspec large volume sample dispersion unit) is preferably selected.

[0012] The resulting spherical and/or spheroidal particles can be classified, for example, by sieving to suit the average particle diameter and reduce the amounts of fine and/or coarse particles. Although handling the particles can lead to a certain degree of disruption, the particles are preferably not subjected to any deliberate comminution process. Preferably, the spherical and/or spheroidal particles are prepared by shaping the spray of a hydrosol, preferably a silica hydrosol. Spherical and/or spheroidal hydrogel particles are suitably subjected to washing and aging processes prior to dewatering to generate adequate surface area and pore volume.

[0013] The silica support should preferably have an average particle size of about 0.1 to 150 microns, typically 10 to 150 microns, preferably about 20 to 100 microns. The silica support preferably should have a large surface area typically greater than about 100 m2/g, preferably greater than about 250 m2/g, more preferably from 300 m2/g to 1000 m2/g. The silica support may preferably be porous and may have a pore volume from about 0.3 to 5.0 ml/g, typically from 0.5 to 3.0 ml/g. Surface area and pore volume can be determined according to the BET volumetric method in British standard BS 435.911 (1984).

[0014] To reduce the level of hydroxyl groups (OH) on the surface, the silica support can advantageously be thermally treated and/or chemically treated. After treatment, the support can be placed in a mixing vessel and mixed with an inert solvent or diluent, preferably a hydrocarbon, and contacted with or without isolation or separation of the solvent or diluent from the catalyst components.

[0015] It is important that the support is dry before impregnation; however, Applicants have disclosed that a mild treatment is most preferred in order to retain the desired hydroxyl group content characteristics on the support surface. Generally, the support can be heated to a temperature of at least 200 °C for up to 24 hours, typically at a temperature of 200 °C to 400 °C (more preferably between 250 °C to 350 °C) for about 2 to 350°C. 20, preferably 4 to 10 hours. The resulting support will be free of adsorbed water and should have a surface hydroxyl content of about 0.6 to 2 mmol/g of support, preferably 1 to 1.6 mmol/g of support.

[0016] A silica suitable for use in the present invention has a high surface area and is amorphous. For example, commercially available silicas are marketed under the trademark ES-70W by PQ Corporation; such ES-70W silica is a microspheroidal support that exhibits the following specifications: an APS Mastersizer comprised between 35 and 47 microns (with D10 of 10.0 microns min and D90 of 85.0 microns max), a pore volume (IPA) between 1.55 and 1.75 ml/g, and a surface area (5 BET points) between 260 and 330 m2/g. Another silica suitable for use in the present invention is a silica commercially available under the trademark SYLOPOL® 2408D by Grace; this is a white powder consisting of amorphous, synthetic silica that exhibits the following specifications: a nitrogen pore volume greater than 1.35 cm3/g; a surface area of between 280 and 355 m2/g (with D10 of 10.0 microns min and D90 of 85.0 microns max).

[0017] The silica support for the catalysts useful in the present invention typically comprises more than 98% by weight of silicon dioxide, preferably more than 99% by weight of silicon dioxide.

[0018] A number of methods are known for determining the amount of hydroxyl groups on silica; for example, using the method described by J.B. Peri and A.L. Hensley, Jr., in J. Phys. Chem, 1968, 72 (8), pp 29262933, or any of the methods described in "The surface chemistry of amorphous silica/Zhuravlev model (Colloids and Surfaces, A: Physiochemical and Engineering Aspects 173 (2000) pages 1-38), by example a thermal mass spectrometric analysis in conjunction with a temperature programmed desorption method, or an infrared method (which can be combined with a thermogravimetric absorption measurement and/or an isotope exchange technique), or a method of determination chemical, such as that described by JJ Fripiat and J. Uytterhoeven (J. Phys. Chem., 1962, 66 (5), pp 800-805, Hydroxyl Content in Silica Gel "Aerosil") For purposes of the present invention and attached claims the amount of hydroxyl groups on silica was measured according to the following method: 2 g of partially dehydrated silica is introduced into a closed vessel under inert atmosphere; 5 ml of CH3MgBr diluted in dibutyl ether is introduced into the vessel under pressure at mosspheric and under a controlled temperature of 25 °C; the resulting mixture is stirred for 10 minutes in order to allow complete reaction between the hydroxyl groups of the silica and the reagent CH3MgBr (in excess) with the corresponding release of CH4 in the gas phase; said CH4 is then measured by a conventional gas chromatography method. The corresponding amount of hydroxyl groups per gram of silica is equal to the amount of methane generated as determined from the GC measurement divided by two (ie, the number of g of silica introduced into the vessel).

[0019] While heating is the most preferred means of partially removing the OH groups inherently present in many vehicles, such as silica, the OH groups can also be partially removed by other means of removal, such as chemical means. For example, a desired proportion of OH groups can be reacted with a suitable chemical agent, such as a hydroxyl-reactive aluminum compound (eg, triethylaluminum).

[0020] The liquid Mg-M complex for the catalysts useful in the present invention is prepared by reacting at least one compound comprising organic oxygen of magnesium with at least one compound comprising organic oxygen of a transition metal.

MAGNESIUM

[0021] The magnesium compound is a compound comprising organic oxygen. The term "magnesium compound comprising organic oxygen" is understood to mean any compound in which an organic radical is attached to a magnesium via oxygen, that is, any compound comprising at least one sequence of magnesium-oxygen-organic radical bonds per atom of magnesium. Organic radicals attached to magnesium via oxygen are generally chosen from radicals comprising up to 20 carbon atoms and more particularly from those comprising up to 10 carbon atoms. Good results are obtained when these radicals comprise from 2 to 6 carbon atoms. These radicals can be saturated or unsaturated, with a branched chain or a straight or cyclic chain. They are preferably chosen from hydrocarbon-comprising radicals and in particular from alkyl (linear or branched), alkenyl, aryl, cycloalkyl, arylalkyl and acyl radicals and their substituted derivatives.

[0022] Magnesium compounds comprising organic oxygen may, in addition to organic radicals linked to magnesium via oxygen, comprise other radicals such as, for example, -OH, -(SO4)i/2, -NO3, - ( PO4)i/3, and -(CO3)1/2. They can also be organic radicals attached directly to magnesium via carbon.

[0023] Mention may be made, among magnesium compounds comprising organic oxygen that may be used, of alkoxides (such as ethoxide and cyclohexanoate), alkyalkoxides (such as ethylethoxide), hydroxyalkoxides (such as hydroxymethoxide), phenoxides (such as naphthenate) , or optionally hydrated carboxylates (such as acetate and benzoate). They can also be compounds comprising oxygen comprising organic nitrogen, i.e. compounds comprising organic-nitrogen-oxygen-magnesium radical linkage sequences (such as oximates, in particular, butyl oximate, or salts of hydroxylamine acids, in particular the derived from N-nitroso-N-phenylhydroxylamine), chelated, i.e. compounds comprising organic oxygen, in which magnesium has at least one sequence of normal bonds of the magnesium-oxygen-organic radical type and at least one coordination bond , so as to form a heterocycle in which magnesium is included (such as enolates, in particular acetylacetonate), or silanolates, i.e. compounds comprising radical bond sequences comprising hydrocarbon-silicon-oxygen-magnesium (such as triphenylsilanolate) . Mention can also be made, as examples of magnesium compounds comprising organic oxygen, of those comprising several different organic radicals (such as magnesium methoxyethoxide), complex of alkoxides and phenoxides of magnesium and another metal (such as Mg[Al( OR)4]2) and mixtures of two or more magnesium compounds comprising organic oxygen defined above.

[0024] The use is preferably made, among all magnesium compounds that are suitable, of which only comprise magnesium-oxygen-organic radical bonds per magnesium atom, to the exclusion of any other bond. Magnesium alkoxides are particularly preferred. Best results are obtained with magnesium dialkoxides, in particular magnesium dietoxide.

TRANSITION METAL

[0025] The compound of a transition metal (M) is a compound comprising organic oxygen. The term "compound of a transition metal comprising organic oxygen" is understood to mean any compound in which an organic radical is attached to the transition metal by means of oxygen, i.e. any compound which comprises at least one sequence of radical bonds iron-oxygen-transition metal per transition metal atom. Organic radicals attached to the transition metal via oxygen are generally chosen from radicals comprising up to 20 carbon atoms and more particularly from those comprising up to 10 carbon atoms. Good results are obtained when these radicals comprise from 2 to 6 carbon atoms. These radicals can be saturated or unsaturated, with a branched chain or with a straight or cyclic chain. They are preferably chosen from hydrocarbon-comprising radicals and, in particular, radicals from an alkyl group (linear or branched), alkenyl, aryl, cycloalkyl, arylalkyl and acyl and substituted derivatives thereof.

[0026] The transition metal ("M") is generally chosen from the transition metals of Group 4 or 5 of the Periodic Table.

[0027] The transition metal is advantageously chosen from titanium, zirconium, hafnium and vanadium, or their mixtures. Titanium is particularly preferred. In the case of titanium, zirconium or hafnium use is preferably made of tetravalent transition metal compounds, because they are generally liquid and, in any case, generally soluble and with better solubility than those in which the transition metal has a valence. less than 4. The compounds of a transition metal comprising organic oxygen that can be used may also comprise transition metal-oxygen-transition metal bonds.

[0028] The compounds of a transition metal comprising organic oxygen can be represented by the general formula MOx(OR')m-2x, where M represents the valence transition metal m, R' represents an organic radical as defined above ex is a number such that 0 < x (m-1)/2. Use is preferably made of compounds where x is such that 0 < x < (m-2)/2. It is obvious that transition metal compounds comprising organic oxygen can comprise several different organic radicals.

[0029] Mention may be made, among the compounds of a transition metal comprising organic oxygen, of alkoxides (such as Ti(On-C4H9)4), phenoxides (such as Zr(OC6H5)4), oxyalkoxides (such as HfO (OC2H5)2), condensed alkoxides (such as Ti2(Oi-C3H7)6), carboxylates (such as Zr(OOCCH3)4) and enolates (such as hafnium acetylacetonate).

[0030] Use is preferably made, among all transition metal compounds which are suitable, those which only comprise transition metal-oxygen-organic radical bonds per transition metal atom, to the exclusion of any other bond. Alkoxides are highly suitable. Best results are obtained with titanium or zirconium tetraalkoxides, in particular titanium or zirconium tetrabutoxide.

[0031] Of course, several different magnesium compounds can be used simultaneously. Likewise, several different compounds of a transition metal or several compounds for which the transition metal is different can also be used simultaneously. The first-stage reaction can be carried out by any suitable known method as long as it makes possible the production of a complex in the liquid state. When the magnesium compound and/or the transition metal compound are liquid under the operating conditions of the reaction, it is desirable to carry out the reaction by simply mixing these reactants in the absence of solvent or diluent. However, the reaction can be carried out in the presence of a diluent when the amount of liquid present in the reaction mixture is insufficient to carry the reaction through to completion or when the two reactants are solid under the operating conditions of the reaction.

1st Stage of the COMPLEX

[0032] According to an embodiment of the present invention, the first stage consists of the formation of a liquid Mg-H complex (M represents a transition metal) by reacting at least one magnesium compound comprising organic oxygen with at least one compound comprising organic oxygen of a transition metal. For the purpose of the present invention and appended claims, no chlorinated and/or halogenated compounds were used during this first stage.

[0033] The amount of transition metal compound used is generally defined with respect to the amount of magnesium compound employed. It can vary within a wide range. In general, it is at least 0.06 mol of transition metal present in the transition metal compound for every mol of magnesium present in the magnesium compound, in particular at least 0.6 mol, values of at least 1.5 moles being the preferred values. The amount is normally at most 4 moles of transition metal present in the transition metal compound per mole of magnesium present in the magnesium compound, more specifically at most 3 moles, values of at most 2.5 moles being recommended.

[0034] The temperature at which the magnesium compound and the transition metal compound are brought together in the first stage of catalyst preparation depends on the nature of the reactants and is preferably lower than the decomposition temperature of the reactants and the liquid complex obtained following the reaction. It is generally at least -20 °C, in particular at least 0 °C, temperatures of at least 20 °C being the most common, temperatures of at least 100 °C being preferred. The temperature is generally a maximum of 200 °C, more especially a maximum of 180 °C, temperatures of a maximum of 150 °C being advantageous, for example, of approximately 140 °C.

[0035] The duration of the first stage depends on the nature of the reactants and the operating conditions and is advantageously long enough to produce a complete reaction between the reactants. The duration can generally range from 10 minutes to 20 hours, more specifically from 2 to 15 hours, for example from 4 to 10 hours.

[0036] The pressure under which the first stage reaction is carried out and the rate of addition of the reactants are not critical factors. For reasons of convenience, the reaction is generally carried out at atmospheric pressure; the rate of addition is generally chosen so as not to cause the reaction mixture to heat up sharply due to an eventual self-acceleration of the reaction. The reaction mixture is generally stirred in order to promote its homogenization for the duration of the reaction. The reaction can be carried out continuously or in batch. This first stage of catalyst preparation is preferably carried out between pure compounds of magnesium and transition metal, i.e. in the absence of diluent.

[0037] On completion of the first stage of catalyst preparation, a liquid complex of the magnesium compound and the transition metal compound is collected, which complex can be employed as in the subsequent stage of impregnation of the inorganic support. It may optionally and preferably be diluted in a diluent, preferably an inert diluent, before its subsequent use. The diluent is generally chosen from aliphatic or cycloaliphatic hydrocarbons preferably comprising up to 20 carbon atoms, such as, for example, alkanes, such as isobutane, pentane, hexane, heptane or cyclohexane, or mixtures thereof. Hexane is particularly highly suitable. When diluted, the diluted complex preferably comprises between 5 and 35% by weight of diluent; it is preferably characterized by a viscosity comprised between 4 and 120, more preferably between 5 and 20 mPa.s at 25°C.

2nd stage IMPREGNATION

[0038] Before impregnation, the silica support is preferably diluted with a diluent, preferably an inert diluent. The diluent is generally chosen from aliphatic or cycloaliphatic hydrocarbons preferably comprising up to 20 carbon atoms such as, for example, alkanes such as isobutane, pentane, hexane, heptane or cyclohexane or mixtures thereof. Hexane is particularly highly suitable. When diluted, the diluted silica support preferably comprises between 50 and 90% by weight of diluent, more preferably between 70 and 85% by weight of diluent. The impregnation of the inorganic support by means of the liquid complex in the second stage of preparing the catalyst according to the present invention can be carried out in any suitable manner. It is generally carried out at a temperature of at least -10 °C and which, in addition, does not exceed 150 °C. The impregnation temperature generally rises to 20 °C and at least must not exceed 100 °C. Excellent results are obtained with impregnation temperatures from 25 to 60 °C. The duration and pressure at which the impregnation is carried out are not critical parameters. The impregnation is generally carried out at atmospheric pressure; good results are obtained when the duration of this impregnation is between 2 and 4 hours in order to guarantee a satisfactory homogenization.

[0039] The amount of liquid complex impregnated on the inorganic support is chosen so that the impregnated catalyst support comprises - a magnesium content of preferably at least 1 mmol and at most 2 mmoles of magnesium per gram of silica support , and - a titanium content, preferably at least 2 mmoles and at most 4 mmoles of titanium per gram of silica support.

3rd PRECIPITATION stage

[0040] In the third stage of the preparation of the catalyst according to the present invention the liquid Mg-M complex is precipitated onto silica by means of a halogenated organoaluminum compound. This precipitation stage has the function of reducing the valence of the transition metal and simultaneously of halogenating the magnesium compound and the transition metal compound, that is, replacing the alkoxy groups present in the magnesium compound and in the metal compound transition by halogens, so that the liquid complex obtained in the first stage is precipitated as a solid catalytic composition.

[0041] The halogenated organoaluminum compound is suitably chosen from organoaluminum compounds corresponding to the general formula AlRnX3-n, wherein R is a radical comprising a hydrocarbon, X is a halogen and n is less than or equal to 2.

[0042] The halogenated organoaluminum compound advantageously corresponds to the formula AlRnX3-n, wherein R is a hydrocarbon-comprising radical comprising up to 20 carbon atoms, X is halogen and n is less than or equal to 2. The radical preferably comprises up to 6 carbon atoms. Good results are obtained when R is an alkyl radical (linear or branched), cycloalkyl, arylalkyl, aryl and alkylaryl. Best results are obtained when R represents a linear or branched alkyl radical. X is usually chosen from fluorine, chlorine, bromine and iodine. Chlorine is particularly highly suitable. Preferably, n does not exceed 1.5, more particularly does not exceed 1. Mention may be made, as examples of the halogenated organoaluminium compounds which can be used in the present invention, of aluminum trichloride [AlCl3]], ethylaluminium dichloride [ Al(C2H5)Cl2], ethylaluminiumsesquichloride [Al2(C2H5)3Cl3] and diethylaluminum chloride [Al(C2H5)2Cl]. Ethyl aluminum dichloride or isobutyl aluminum dichloride is preferred.

[0043] The treatment by means of a halogenated organoaluminum compound in the third stage of precipitation of the catalytic composition on the inorganic support can be carried out by any suitable known means and preferably by gradually adding the halogenated organoaluminum compound to the inorganic support impregnated with the complex liquid obtained from the first stage.

[0044] Prior to said treatment, the halogenated organoaluminium compound may advantageously be diluted in a diluent, preferably an inert diluent. The diluent is generally chosen from aliphatic or cycloaliphatic hydrocarbons, preferably comprising up to 20 carbon atoms, such as, for example, alkanes, such as isobutane, pentane, hexane, heptane or cyclohexane, or mixtures thereof. Hexane is particularly highly suitable. When diluted, the dilute halogenated organoaluminium compound preferably comprises between 40 and 90% by weight of diluent, more preferably between 50 and 80% by weight of diluent.

[0045] The amount of halogenated organoaluminum compound to be employed depends on the amounts of the magnesium compound and the transition metal compound used and is advantageously sufficient to produce the desired degree of reduction and the desired degree of halogenation. In practice, it is not advantageous to employ an amount greater than the minimum amount necessary to achieve complete reduction and, if appropriate, complete halogenation as any excess employed results in an increase in the aluminum content in the catalyst, which is undesirable. . The amount is generally at least 1 mole of aluminum for each mole of magnesium used, preferably at least 1.5 moles, values of at least 2 moles being most usual; the amount is commonly at most 12 moles of aluminum per mole of magnesium used, in particular at most 8 moles, values of at most 6 moles being advantageous. The amount is generally at least 0.5 mol of aluminum per mol of transition metal used and preferably at least about 0.75 mol, values of at least 1 mol being most usual; the amount is commonly at most 6 moles of aluminum per mole of transition metal employed, in particular at most 4 moles, values of at most 3 moles being advantageous.

[0046] The temperature at which the precipitation stage of the liquid complex is carried out is advantageously lower than the boiling temperature, at normal pressure, of the halogenated organoaluminium compound. It is generally at least -20 °C, more particularly at least 0 °C, temperatures of at least 20 °C being recommended. The temperature generally does not exceed 150 °C, more particularly does not exceed 100 °C, temperatures of at most 80 °C being the most usual.

[0047] The duration of the precipitation stage of the liquid complex is preferably sufficient to produce a complete precipitation. It can range from 1 minute to 10 hours, more specifically from 10 minutes to 8 hours, for example from 0.5 to 5 hours.

[0048] The pressure under which the liquid complex precipitation step is carried out is not a critical factor. For reasons of convenience, the operation is generally carried out at atmospheric pressure. The rate of addition of reactants is generally chosen so as not to cause the reaction mixture to heat up sharply due to an eventual self-acceleration of the reaction. The reaction mixture is generally stirred, in order to promote its homogenization, for the duration of the reaction. The reaction can be carried out continuously or in batch.

[0049] After completion of the liquid complex precipitation stage by means of a halogenated organoaluminium compound, a catalyst is collected which is composed of a homogeneous precipitate (the constituents being co-precipitated from a liquid complex) on an inorganic support , of an essentially amorphous mixture of a magnesium halide and a transition metal halide. They are chemically bonded complexes, produced from chemical reactions, and not the result of mixtures or adsorption phenomena. This is because it is impossible to dissociate one or the other of the constituents of these complexes using purely physical separation methods.

[0050] The precipitation stage of the liquid complex can be advantageously followed by a maturation treatment, the function of which is to continue the precipitation reaction and make it possible to obtain a catalyst that has a better resistance to aging. Maturation is carried out at a temperature generally equivalent to or higher than that at which precipitation occurs (for example, between 40 °C and 65 °C). It is carried out for a non-critical period, generally ranging between 5 minutes and 12 hours, preferably for at least 0.5 hour.

PRECURSOR COMPOSITION OF THE CATALYST

[0051] The present invention also provides a catalyst composition supported on silica that is useful in the polymerization of olefin, said composition being characterized by - a SiO2 content not greater than 70% by weight, - a transition metal content (M) comprised between 2.5 and 9.1% by weight; - a magnesium content of between 0.5 and 3.3% by weight; - an aluminum content of between 0.3 and 5% by weight and - a chlorine content of between 5 and 30% by weight; and wherein - said silica support has, before the addition of catalytically active ingredients, a residual surface hydroxyl content comprised between 0.6 and 2 mmol/g of silica, and - the molar ratio of transition metal (M) to magnesium is between 0.3 and 2.5.

[0052] The present invention also provides a catalyst composition which is useful in the polymerization of olefin, said composition being characterized by - a SiO2 content not greater than 70% by weight, - a transition metal (M) content comprised between 2 .5 and 9.1% by weight; - a magnesium content of between 0.5 and 3.3% by weight; - an aluminum content of between 0.3 and 5% by weight and - a chlorine content of between 5 and 30% by weight; and said composition being obtained or obtainable by a preparation process comprising - in a first stage, the formation of a liquid Mg-M complex by reacting at least one magnesium compound comprising organic oxygen with at least one transition metal compound comprising organic oxygen, - in a second stage, the impregnation of a silica support by means of said liquid Mg-M complex, and - in a subsequent stage, the precipitation of said liquid Mg-M complex onto silica by means of a halogenated organoaluminium compound, in which said silica support has, before impregnation of the liquid Mg-M complex, a residual residual hydroxyl content of between 0.6 and 2 mmol/g of silica.

[0053] The SiO2 content of the catalyst composition is not more than 70% by weight; it is preferably more than 40% by weight, more preferably more than 50% by weight.

[0054] The transition metal (M) content of the catalyst composition is comprised between 2.5 and 9.1% by weight, preferably between 3 and 8% by weight.

[0055] The magnesium content of the catalyst composition is comprised between 0.5 and 3.3% by weight, preferably between 1.5 and 2.5% by weight.

[0056] The molar ratio between transition metal (M) and magnesium of the catalyst composition is preferably comprised between 0.3 and 2.5, more preferably comprised between 0.4 and 2.0, more preferably comprised between 0. 75 and 1.8.

[0057] The aluminum content of the catalyst composition is comprised between 0.3 and 5% by weight, preferably between 0.5 and 2.5 % by weight.

[0058] The chlorine content of the catalyst composition is comprised between 5 and 30% by weight, preferably between 8 and 22% by weight.

[0059] The weight ratio (solid catalytic composition)/(silica support) is preferably comprised between 0.4 and 1.3, more preferably between 0.5 and 1, more preferably between 0.55 and 0.8.

[0060] In an alternative embodiment according to the present invention, an electron donor is added to the claimed catalyst and preparation process; examples of such an electron donor can be found in EP 0.703247, the contents of which are hereby incorporated by reference. However, and this is a preferred embodiment according to the present invention, no electron donor is used in the catalyst composition and catalyst preparation according to the present invention.

CO-CATALYST

[0061] The catalysts according to the invention are particularly suitable for the polymerization of olefins. The invention also relates to the use of these catalysts, in combination with a cocatalyst selected from organometallic compounds of a metal from Groups 1, 2, 12, 13, and 14, in the polymerization of olefins. The organometallic compound which serves as the catalyst activator and which is commonly known as the "co-catalyst" can be chosen from organometallic compounds of lithium, magnesium, zinc, aluminum or tin. Best results are obtained with organoaluminium compounds.

[0062] Use can be made, as organometallic compound, of fully alkylated compounds with straight or branched alkyl chains comprising up to 20 carbon atoms, such as, for example, n-butyl lithium, diethylmagnesium, diethylzinc, tetraethyltin, tetrabutyltin and trialkylaluminum. Alkylmetal halides where the alkyl radicals also comprise up to 20 carbon atoms, such as diisobutylaluminum hydride and trimethyltin hydride. Alkylmetal halides in which the alkyl radicals also comprise up to 20 carbon atoms, such as ethylaluminum squichloride, diethylaluminum chloride and diisobutylaluminum chloride, are also suitable. Use can be made of organoaluminum compounds obtained by reacting trialkylaluminum or dialkylaluminum hydrides, the radicals of which comprise up to 20 carbon atoms, with diolefins comprising from 4 to 20 carbon atoms and, more particularly, the compounds known as isoprenylaluminums.

[0063] Preference is generally given to trialkylaluminums in general and in particular to those with linear alkyl chains comprising up to 18 carbon atoms, more particularly from 2 to 8 carbon atoms. Aluminum triethyl and aluminum triisobutyl addition of the activator and the separately supported catalyst for are preferred.

[0064] The catalyst can be activated in situ by the polymerization medium. It is also possible to combine catalyst precursor and activator prior to introduction into the polymerization medium, for example, for up to about 2 hours at a temperature of about -40°C to about 80°C.

[0065] An adequate amount of activator activation can be used. The number of moles of activator per gram of titanium atom in the catalyst can be, for example, from about 1 to about 100 and is preferably greater than about 5.

POLYMERIZATION

[0066] The catalyst as described above can be used in a suspension phase process. A suspension process typically uses an inert hydrocarbon diluent and temperatures from about 0°C to a temperature just below the temperature at which the resulting polymer becomes substantially soluble in the inert polymerization medium. Suitable diluents include toluene or alkanes such as hexane, propane or isobutane. Preferred temperatures are from about 30 °C to about 200 °C, but preferably from about 50 °C to 125 °C. Closed loop reactors are widely used in suspension polymerization processes. In a closed loop reactor the suspension is typically circulated in the reactor by means of a pump or an agitator. Liquid closed loop reactors are particularly well known in the art and are described, for example, in US patents 3,152,872, 3,242,150 and 4,613,484. Additional references of suspended operations in which the present invention can advantageously be used are W02007138257 and W02006056763. Closed loop suspension polymerization is typically carried out at temperatures in the range of 50 to 125 °C and at pressures in the range of 1 to 100 bar (100 to 10000 Pa). The product suspension, comprising polymer and diluent and in most cases also the olefin catalyst, monomer and comonomer can be discharged intermittently or continuously.

[0067] The present invention is particularly useful in a continuous gas phase process for polymerization, at a pressure of 10 to 500 psi (68.95 to 3447.4 kPa), of a mixture comprising from 0 to 60% by mol. of hydrogen, from 0 to 35 mol% of one or more C3-8-olefins, from 15 to 100 mol% of ethylene and from 0 to 75 mol% of an inert gas such as N2, conducted at a temperature of 50 °C to 125 °C, preferably less than 115 °C, in the presence of a catalyst and a co-catalyst as described above.

[0068] Thus, the present invention also provides the use of a catalyst system in a continuous gas phase process for polymerization, at a pressure of 10 to 500 psi (68.95 to 3447.4 kPa), of a mixture comprising from 0 to 60% by mol of hydrogen, from 0 to 35% by mol of one or more C3-8-olefins, from 15 to 100% by mol of ethylene and 0 to 75% by mol of an inert gas, such as as N2, conducted at a temperature of 50 °C to 125 °C, preferably less than 115 °C, wherein the catalyst system includes a silica supported catalyst and an organoaluminium cocatalyst, said supported catalyst comprising a chlorinated-precipitate Mg-M complex on silica, characterized by - a SiO2 content not greater than 70% by weight, - a transition metal (M) content of between 2.5 and 9.1% by weight; - a magnesium content of between 0.5 and 3.3% by weight; - an aluminum content of between 0.3 and 5% by weight and - a chlorine content of between 5 and 30% by weight; and in which - said silica support was said, before the addition of catalytically active ingredients, a residual surface hydroxyl content comprised between 0.6 and 2 mmol/g of silica, and - the molar ratio of transition metal (M ) for magnesium is preferably comprised between 0.3 and 2.5.

[0069] The above supported catalyst is preferably obtained or obtainable by a preparation process comprising - in a first stage, the formation of a liquid Mg-M complex by reacting at least one magnesium compound comprising organic oxygen with at least one compound comprising transition metal oxygen, - in a second stage, the impregnation of a silica support by means of said liquid Mg-M complex, and - in a subsequent stage, the precipitation of said liquid Mg-M complex onto the silica by means of a halogenated organoaluminium compound, on which said silica support has, before impregnation with the liquid Mg-M complex, a residual surface hydroxyl content of between 0.6 and 2 mmol/g of silica. Gas phase polymerization and in particular gas phase fluidized bed polymerization of ethylene polymers has been known for some time. A broad overview of these types of processes is defined in the document "Gas Phase Ethylene Polymerization: Production Processes, Polymer Properties, and Reactor Modeling" by TuyuXie, Kim B. McAuley, James CC Hsu, and David W. Bacon, Ind. Eng. Chem Res. 1994, 33, 449-479.

[0070] Generally, a monomer feed comprising at least ethylene and optionally one or more C3-8-olefins is fed to a stirred bed reactor or fluidized bed in gas phase. The mixture of monomers optionally together with hydrogen and/or an inert gas are fed to the fluidized bed. In a fluidized bed reactor, the gas velocity is sufficient to suspend the bed in the fluid flow of monomer and other components. In an agitated bed reactor agitated mechanical agitation serves to help suspend the bed. Generally, a fluid bed reactor is vertical and a stirred bed reactor is horizontal. Concurrently with the monomers a co-catalyst and a supported catalyst are fed to the bed. The monomer that passes over the catalyst polymerizes on the catalyst and in the catalyst pores, causing the particle to increase in size and rupture. The resulting polymer particle continues to grow as it resides in the reactor. In a stirred tank reactor the bed is stirred to a discharge section and leaves the reactor. In a fluidized bed the reactor typically has a narrower section to keep the fluid (gas) velocity high enough to fluidize the bed. There is an expanded zone at the top of the reactor to reduce the velocity of the gas passing through the reactor so that the polymer/catalyst particles return to the bed. Discharge is from the bed zone in the reactor.

[0071] In both the fluidized bed and stirred bed the polymer particles removed from the reactor are degassed to remove all volatile material and the resulting polymer (with entrained catalyst) can then be further treated (e.g., added stabilizers and pelletized if necessary).

[0072] In the reactor the gas phase typically comprises the monomers, an equilibrium gas such as nitrogen, a molecular weight control agent such as hydrogen, and depending on the process, possibly a condensable liquid (i.e., the condensation mode as described in US Patent 4,543,399 issued September 24, 1985 to Jenkins III et al.; 4,588,790 issued May 15, 1986 to Jenkins III et al.; and the so-called super condensation mode as disclosed in US patent 5,352,749 issued October 4, 1994 to DeChellis et al filed by Exxon Chemical Patents Inc., and US patent 5,436,304 issued July 25, 1995 to Griffin et al filed by Exxon Chemical Patents, Inc.). Additional references of gas phase operations in which the present invention can be advantageously used are WO9428032, W02010037650 and international patent application number PCT/EP2011/070280.

[0073] The condensable liquid may be a condensable monomer, for example, but-1-ene, hex-1-ene, 4-methylpent-1-ene, cyclooctene, 1-pentene or octene used as a comonomer , and/or an optional inert condensable liquid, for example inert hydrocarbon(s) such as C4-C8 alkane(s) or cycloalkane(s), particularly butane, pentane or hexane. The partial pressure of said condensable liquid under reaction conditions is preferably greater than 2 bar (200 kPa).

[0074] The present invention is advantageously used in very high space temp yield. The space-time reduction ("STY") is expressed in [kg/(m3 x h)] is well known and represents the weight of polymer produced per unit time and per unit volume of the reactor. STY equal to or greater than 100 kg/(m3 x h) and up to 120 kg/(m3 x h) are preferred.

[0075] The reactor mixture comprises from 0 to 60% by mol of hydrogen, from 0 to 35% by mol of one or more C3-8-olefins, from 15 to 100% by mol of ethylene and 0 to 75% by mol of an inert gas such as N2. Copolymerizable olefins include butene (1-butene), 4-methyl-1-pentene, pentene, hexene (1-hexene), and octene (1-octene), although it can be difficult to maintain significant amounts of octene in the gas phase. The polymer can have a density of from 0.905 to 0.965 g/cm3, typically from about 0.910 to about 0.960 g/cm3.

[0076] Fluidized bed gas phase reactors for producing polyethylene are generally operated at temperatures from about 50 °C to about 125 °C (provided the polymer adhesion temperature is not exceeded), preferably at about 75 °C to about 110 °C and at pressures typically not exceeding 3447 kPa (about 500 psi), preferably not greater than about 2414 kPa (about 350 psi).

[0077] Polymerization additives can also be advantageously added during the polymerization process according to the present invention. Activity enhancing additives are preferred. For example, the halogenated hydrocarbon compound may advantageously be introduced during polymerization in amounts effective to increase the activity of the catalyst, the amount preferably being such that the q molar amount of the halogenated hydrocarbon compound to that of the introduced catalyst transition metal in the polymerization medium is greater than 0.001 and less than 10. Said amount of halogenated hydrocarbon compound can also be advantageously controlled such that the molar ratio of halogenated hydrocarbon compound to cocatalyst is comprised between 0.03 and 0.2 . The halogenated hydrocarbon compound may be a saturated mono or polyhalogenated hydrocarbon, and is preferably selected from the group consisting of methylene chloride, chloroform, carbon tetrachloride, 1,1,1-trichloroethane and 1,2-dichloroethane; monoalkyl chloride (R-Cl) such as, for example, butyl chloride are preferably used. Examples of these can be found in EP 0.703246, EP 1350.802 and WO 0228919.

Typically, the resulting polymer will comprise from 85 to 100% by weight of ethylene and from 0 to 15% by weight of one or more C3-8-olefins. The polymer must have a molecular weight (average weight, Mw) greater than 50,000 Da.

[0079] The resulting polymers can be used in a number of applications, such as film extrusion, both blown or cast film extrusion, and both injection and rotational molding applications. Typically, the polymer can be blended with the usual additives including thermo- and photo-stabilizers, such as hindered phenols; ultraviolet light stabilizers, such as hindered amine light stabilizers (HALS); processing aids such as fatty acids or their derivatives and fluorinated polymers optionally together with low molecular weight polyethylene glycol esters.

[0080] The present invention will now be illustrated by the following non-limiting examples. It will be evident from the results obtained in the examples using the catalysts according to the present invention in gas phase polymerization, that such results show improved catalyst productivity, improved hydrogen response and improved activity profile; while not wishing to be limited to that explanation, applicants believe that it is the combination of the catalyst composition together with its method of preparation that enables such results to be obtained. Examples Catalyst Preparations 1.Catalysts of the invention (IC1 and IC2) a. Complex preparation: magnesium dietoxide was reacted under stirring for 7 hours at 140°C with titanium tetrabutoxide in amounts such that the titanium to magnesium molar ratio was equal to 2. The resulting complex is diluted in hexane before subsequent use; the diluted complex comprises 15% by weight of hexane. B. 10,000 g of ES70W silica from PQ Corporation is calcined at 300°C under nitrogen for 6 hours. The resulting silica exhibits a residual surface hydroxyl content of 1.56 mmol per gram of silica. It is diluted with 55,000 ml of purified hexane in a stainless steel reactor equipped with an impeller. ç. Impregnation: 13,700 ml of the diluted complex (homogeneous mixture of Mg(OEt)2 and Ti(OBu)4, with Ti/Mg = 2 mol/mol diluted in hexane at 85% concentration) are added to the reactor under agitation. The silica-based suspension is stirred at 350 rpm and the temperature is adjusted to 50°C for 3 hours. d. Precipitation: A chlorinating agent (isobutyl aluminum dichloride (IBADIC) for IC1 catalyst, ethylaluminium dichloride (EADC) for IC2 catalyst) at 50% by weight concentration in hexane is added over 1 hour with one setting of temperature to control the exotherm of the reaction set at 40 °C. The amount of chlorinating agent is selected such that it corresponds to an Al/Mg ratio of 4.2 mol/mol for the catalyst IC1 and 6.5 mol/mol for the catalyst IC2. At the end of the reaction, the catalyst suspension is aged at the same temperature (40°C) for 1 hour. After aging of the catalyst, the reactor is cooled to room temperature and purified hexane is added to the reactor to set the volume to 250,000 ml. The stirrer is then stopped and the catalyst suspension is decanted for 30 minutes, the hexane supernatant (where the chlorination reaction by-products are diluted) is evacuated with a dip tube to the solids level (~125,000 ml). Fresh hexane is added (~125,000 ml) to recover a final volume of 250,000 ml and the suspension is stirred for 10 minutes. The decant/extraction sequence is repeated 5 times with each addition to each fresh hexane period. and. At the end of the catalyst wash sequence, the catalytic suspension is transferred from the reactor to a drying equipment under a nitrogen atmosphere and dried under vacuum (10-3 bar ()) for 4 hours. f. Details of the preparation of ICl and IC2 catalysts and their compositions are shown in Table 1. Table 1

2. Comparative catalyst (C1)

[0081] The catalyst is a silica supported catalyst which is the same as that disclosed in comparative example 1 of WO99/05187 (1 mmol DBM/g silica, 0.44 mmol TEOS/g silica, 1 mmol TiCl 4 /g silica).

Polymerizations Manufacture of a gas phase copolymer of ethylene and 1-butene

[0082] The operation was carried out in a gas phase polymerization reactor consisting essentially of a vertical cylinder with a diameter of 74 cm and a height of 6 meters, with a separation chamber above it, equipped at its bottom with a grid of fluidization and a recycling conduit connecting the top of the separation chamber to the bottom of the reactor, the recycling conduit being equipped with a cyclone, a heat exchanger, a separator, a compressor and feed conduits for ethylene, for 1- butene, for hydrogen and for pentane. The reactor was also equipped with a catalyst feed conduit and a conduit for extracting the copolymer.

[0083] The reactor contained a fluidized bed of polymer particles being formed, which had a height of 5.4 meters and through which a stream of reaction gas mixture, which had an ascending velocity of 50 cm/s, was passed. absolute pressure and at a temperature as indicated in the table below.

[0084] The compositions of the reaction gas mixture are indicated in the Table. The reactor was fed with the previously prepared catalyst. It was also fed separately with triethylaluminum.

RH2 = pH2/pC2 RC4 = pC4/pC2 Produtividade é fornecida em grama de polímero por grama de catalisador.[0085] Under these conditions a copolymer was extracted. The polymer properties are shown in table 2. Said results show the improved catalyst productivity and the improved hydrogen response obtained using the catalysts according to the present invention in gas phase polymerization. Table 2

RH2 = pH2/pC2 RC4 = pC4/pC2 Productivity is given in grams of polymer per gram of catalyst.

Claims (17)

1. Process for the preparation of an alpha-olefin polymerization catalyst composition characterized by comprising - in a first stage, the formation of a liquid Mg-M complex (M is a transition metal) in the absence of a halogen-containing compound by reacting at least one magnesium compound comprising organic oxygen with at least one transition metal compound comprising organic oxygen, - in a second stage, impregnating a silica support by means of said liquid Mg-M complex, and - in a subsequent stage, the precipitation of said liquid Mg-M complex on silica by means of a halogenated organoaluminium compound, wherein - during the first stage reaction, the molar amount of transition metal M added per mole of magnesium is comprised between 0.06 and 4, and - said silica support has, before impregnation of the liquid Mg-M complex, a residual surface hydroxyl content of between 0.6 and 2 mmol/g of silica. 2. Process according to claim 1, characterized in that the silica support has, before impregnation of the liquid Mg-M complex, a residual surface hydroxyl content of between 1 and 1.6 mmol/g of silica. 3. Process according to claim 1 or 2, characterized in that it comprises - in the first stage, the formation of a liquid Mg-M complex (M is a transition metal) by the reaction of at least one magnesium compound comprising oxygen organic with at least one compound of a transition metal comprising organic oxygen, wherein use is made of magnesium compounds which comprise only magnesium-oxygen-organic radical bonds per magnesium atom, to the exclusion of any other bond and wherein use is made of transition metal compounds which comprise only transition metal-oxygen-organic bonds per transition metal atom, to the exclusion of any other bond. 4. Process according to any one of claims 1 to 3, characterized in that the impregnation of the complex (second stage) is carried out on silica that has been subjected to a heat treatment step at a temperature of at least 200 ° C for up to 24 hours. 5. Process according to any one of claims 1 to 4, characterized in that the magnesium compound comprising organic oxygen is a magnesium dialkoxide, in particular magnesium dietoxide. 6. Process according to any one of claims 1 to 5, characterized in that the compound of a transition metal comprising organic oxygen is a titanium tetra-alkoxide, a zirconium tetra-alkoxide, or a mixture thereof. 7. Process according to claim 5, characterized in that the compound of a transition metal comprising organic oxygen is a titanium tetra-alkoxide. 8. Process according to claim 6 or 7, characterized in that the alkoxide is a butoxide. 9. Process according to any one of claims 1 to 8, characterized in that during the impregnation stage, the amount of liquid complex impregnated on the inorganic support is selected in such a way that the impregnated silica support comprises - a content of magnesium comprised between 1 mmol and 2 mmoles of magnesium per gram of silica support, and - a titanium content comprised between 2 mmoles and 4 mmoles of titanium per gram of silica support. 10. Process according to any one of claims 1 to 9, characterized in that the halogenated organoaluminium compound used in the precipitation step is chosen from the organoaluminium compounds corresponding to the general formula AlRnX3-n, where R is a hydrocarbon-comprising radical comprising up to 20 carbon atoms, X is halogen and n is less than or equal to 2. 11. Process according to claim 10, characterized in that the organoaluminum compound is chosen from aluminum trichloride [AlCl3], ethylaluminum dichloride [Al(C2H5)Cl2], ethylaluminum and squichloride [Al2(C2H5Cl3], chloride diethylaluminum [Al(C2H5)2Cl], or a mixture thereof. 12. Process according to any one of claims 1 to 11, characterized in that during the precipitation stage, the molar amount of aluminum added - per mol of magnesium used is between 1 and 12, and - per mol of transition metal M used is between 0.5 and 6. 13. A silica-supported catalyst composition which is useful in the polymerization of olefins characterized by - a SiO2 content not greater than 70% by weight, - a transition metal (M) content of between 2.5 and 9.1% in Weight; - a magnesium content of between 0.5 and 3.3% by weight; - an aluminum content of between 0.3 and 5% by weight and - a chlorine content of between 5 and 30% by weight; and wherein - said silica support has, before the addition of catalytically active ingredients, a residual surface hydroxyl content comprised between 0.6 and 2 mmol/g of silica, and - the transition metal molar ratio (M) for magnesium it is between 0.3 and 2.5. Catalyst composition according to claim 13, characterized in that it is obtainable by a preparation process as defined in any one of claims 1 to 12. 15. Catalyst composition according to claim 13 or 14, characterized in that the silicon dioxide content of the catalyst composition is more than 40% by weight. Use of a catalyst composition as defined in any one of claims 13 to 15 together with a co-catalyst in a continuous suspension phase or a continuous gas phase process characterized in that it is for the polymerization of olefins, wherein the cocatalyst is chosen from organometallic compounds of a Group 1, 2, 12, 13, and 14 metal. 17. Gas-phase process for the (co)-polymerization of olefins characterized in that it is in the presence of a polymerization catalyst supported on silica having the following characteristics: - an SiO2 content not greater than 70% by weight, - a content of transition metal (M) comprised between 2.5 and 9.1% by weight; - a magnesium content of between 0.5 and 3.3% by weight; - an aluminum content of between 0.3 and 5% by weight and - a chlorine content of between 5 and 30% by weight; wherein - said silica support has, before the addition of catalytically active ingredients, a residual surface hydroxyl content comprised between 0.6 and 2 mmol/g of silica, and - the molar ratio of transition metal (M) to the magnesium is comprised between 0.3 and 2.5, and where the productivity is greater than 10,000 g of polymer per gram of catalyst, the space-time yield is greater than 100 kg/m3/h and the partial pressure of condensable hydrocarbon under reaction conditions it is greater than 2 bar (200 kPa).